OpenSSL | Load Additional Functions

By Default Indy defines the most common openssl functions needed to encrypt the communications, but sometimes you need more functions for encrypt, signing... you can use the method IdOpenSSLSetLoadFuncsCallback to assign a callback for loading  additional OpenSSL functions dynamically.

 

IdOpenSSLSetLoadFuncsCallback

TIdLoadSSLFuncsCallback = procedure(hIdSSL: TIdLibHandle; hIdCrypto: TIdLibHandle; const FailedLoadList: TStringList);

This is a procedure type that serves as a callback, it takes three parameters:

 

• hIdSSL: TIdLibHandle - Handle to the loaded SSL library.
• hIdCrypto: TIdLibHandle - Handle to the loaded Crypto library.
• FailedLoadList: TStringList - A list of functions that failed to load.

The purpose of this callback is to allow the user to perform custom processing when OpenSSL functions are being loaded, such as logging failed function loads or handling errors.

 

 

IdOpenSSLSetUnLoadFuncsCallback

 

TIdUnLoadSSLFuncsCallback = procedure();

It serves as a callback for unloading SSL functions.This is useful for performing cleanup when OpenSSL libraries are being unloaded.

 

 

How to load custom function

Find below a simple example of how to load the function EVP_PKEY_CTX_set_rsa_padding using the callbacks.

 

var
  EVP_PKEY_CTX_set_rsa_padding : function(ctx: PEVP_PKEY_CTX; pad: Integer): Integer; cdecl;

procedure DoOpenSSLLoadFuncsCallback(hIdSSL: TIdLibHandle; hIdCrypto:
    TIdLibHandle; const FailedLoadList: TStringList);
begin
  @EVP_PKEY_CTX_set_rsa_padding := LoadLibFunction(hIdCrypto, 'EVP_PKEY_CTX_set_rsa_padding');
end;

procedure DoOpenSSLUnLoadFuncsCallback;
begin
  @EVP_PKEY_CTX_set_rsa_padding := nil;
end;

IdOpenSSLSetLoadFuncsCallback(DoOpenSSLLoadFuncsCallback);
IdOpenSSLSetUnLoadFuncsCallback(DoOpenSSLUnLoadFuncsCallback);